1. Field of Invention
This invention relates to mechanical drive systems, the application described is for an electric vehicle.
2. Prior Art
Vehicles powered by internal combustion engines move several parts in the engine and driveline before providing power to the wheels. Typically, flywheels, clutch assemblies, transmission shafts, gear clusters, differential gears, and final drive shafts are among these parts. Front wheel drive systems can be more efficient and the addition of automatic transmissions can be less efficient.
In all cases power and motion are translated from different rotational planes and sometimes directions before finally being used. Much of the energy required to move these parts and translate this motion is lost.
Efficiently Transmitting Vehicle Drive Power: One attempt to improve the efficiency of transmitting vehicle drive power to the wheels is U.S. Pat. No. 6,179,078 B1 Belloso (2001). This ‘Fuel Efficient and Inexpensive Automobile’ has independent internal combustion engines mounted at each rear wheel. In this way power is transmitted separately to each of the rear wheels to drive the vehicle forward through chains, belts and torque converters. The vehicle uses electric motors to power it in reverse. Both engines are used for acceleration. To improve fuel efficiency only one engine is used to maintain a desired speed.
This theory of operation seems reasonable. But synchronizing the operation of the separate engine drives would be difficult. An overpowered or underpowered engine or, an engine problem could unintentionally steer the vehicle. The power lost in the torque converters and the drive systems could be significant. High load or long distance rear wheel drive may not be possible.
Other improvements for efficiently transmitting vehicle drive power are shown in several electric and hybrid systems. In the following examples electric motors are directly coupled to the drive wheels or, are, part of the drive wheels. U.S. Pat. Nos.: 5,418,437 Couture et al, (1995), 5,921,338 Edmondson (1999), 6,880,654 B2 Plishner (2005), US 2005/0045392 Maslov et al. (2005), US 2006/0180365 Handa et al. (2006). But these designs lead to another problem, suspension arms with a high un-sprung weight.
High Un-Sprung Weight Suspension Arms: High un-sprung weight suspension arms are slower to move. Once in motion they are more difficult to control. And they are slower to return to their original position and be ready for additional movement.
For example, when potholes are driven over in the roadway the suspension arm(s) and drive wheel(s) are slow to move and find the new bottom. When bumps (small hills) are driven over in the roadway the suspension arm(s) and wheel(s) are slow to return to the roadway if they become airborne.
The slow movement of the high un-sprung weight suspension arm makes the drive wheel(s) stay in the air for a longer period of time. When wheels are not contacting the roadway they provide no traction. Vehicles with high un-sprung weight suspension arms hold the road poorly.